Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $219.81   7.390%   $236.054   $236.05   $236.05   $236.10  
  Purchase #2 $124.38   11.239%   $138.3591   $138.36   $138.35   $138.40  
  Purchase #3 $48.71   3.439%   $50.3851   $50.39   $50.40   $50.40  
  Purchase #4 $192.36   8.146%   $208.0296   $208.03   $208.05   $208.00  
  Purchase #5 $232.69   3.227%   $240.1989   $240.20   $240.20   $240.20  
  Purchase #6 $32.33   5.432%   $34.0862   $34.09   $34.10   $34.10  
  Purchase #7 $99.91   7.332%   $107.2354   $107.24   $107.25   $107.20  
  7 purchase totals = $950.19       $1,014.3483   $1,014.36   $1,014.40   $1,014.40